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統計： A(27), B(123), C(96), D(22), E(0) #428369

詳解 (共 1 筆)

#695613
(4/5)^n+(3/5)^n    無窮及數的和=A1/(1-R)=(4/5)/(1-4/5)+(3/5)/(1-3/5)=11/2

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